Watch synchronizer



Feb. 9, 1937. A' w 2,069,909

WATCH SYNCHRONI ZER Filed 001;. 8. 1931 Wz' inessea:

Patented Feb. 9, 1937 UNITED STATES PATENT OFFICE Bjorndal. J any City, N. 1.

Application October 8, 1931, Serial No. 587.843

3 Claims.

My invention relates to improvements in means for the determination of errors in watches, clocks and similar horological instruments and thereby enable the watch maker to set such instruments to indicate correct time. In accordance with present practice a skilled watch maker must observe and adjust a watch over a period of several days to get it correctly adjusted. With my present instrument this otherwise complicated adjustment can be undertaken in a few minutes and with a very high degree of accuracy. It is possible with my apparatus'to set a watch so as not to vary more than one second in twenty-four hours, which for all practical purposes is quite satisfactory. Contrary to other devices using the sound of the tick" of the watch the present invention relates to a stroboscopic device of special design which enables the operator to visually observe the leading, lagging or synchronism of the tested instrument as compared to a standard timing device giving accurate time. The visual observation has the advantage that it is more reliable and easier to operate than any method depending upon the car. My apparatus further has the advantage that by a special arrangement the watch to be set may be tested in any desirable angle or position, and with or without the case, thus enabling a quick location of any faults. This is very important as very few watches will keep correct time when placed in diflerent positions. Another purpose of my invention is to produce a small handy instrument which is instantly ready for service and which takes little space in the watch makers kit. A further purpose is to provide an instrument readily portable and suitable to be carried in the watch makers kit when repairing clocks and watches in institutions, etc. and when repairing and adjusting industrial time devices such as time switches for street lighting systems, process control clocks, etc. Other purposes will be evident from the following specification and claims.

Fig. 1 shows a plan view of the complete device which I have called a watch synchronizer.

Fig. 2 is a side elevation of the same device in its preferred form.

Fig. 3 shows a sectional elevation along the line 3-3 in Fig. 1.

Fig. 4 is a sectional 4-4 in Fig. 1.

In Fig. 1 is shown the telescope I mounted on the drum housing 2 with cover 3. On the telescope is mounted the split tube 4 which my be freely turned radially and which holds another split tube 5 forming a bearing for the arm I the elevation along the line other end of which rests in another bearing 1 on which is mounted the watch holder 8 with spring 9. The arm 3 may thus be revolved in bearings 5 and I until the holder 3 is in any desirable position. In Fig. 1 is also shown the lamp III with socket H and cord l2 connecting through a switch to the outgoing cord I3. Further is shown the dial it with pointer I3 and the starting button H. The dial I5'is an integral part of easing 2; in the preferred embodiment shown in Fig. 1 this dial is an etched plate soldered to the lower edge of easing 2 as indicated in Fig. 3. It is to be noted in Fig. 1 that the telescope I is placed eccentricaliy to the housing 2, the reasons herefore will be explained below.

In Fig. 2 is shown a side elevation of the same device as described in Fig. 1. Further parts to be noted are the motor housing l1 and the switch I8. The latter serves to switch on the current from the lamp and motor when the device is not in use. The lamp I0 is a small concentrated filament lamp which focuses its light on the balance wheel of the watch to be held in holder 8. This lamp may be supplied with current directly from the same source as the motor or it may be supplied at a lower voltage from a coil forming a secondary winding with the coil of the motor. The motor housing is open toward the bottom and this opening is covered up with the cover I! which also forms the foot on which the instrument stands.

In Fig. 3 is shown a sectional elevation through the telescope, stroboscopic drum and motor. It shows how the telescope l is supplied with two lenses 20 and 2| which are optically so designed as to focus on the balance wheel of the watch to be held in holder 8. These lenses are held in ferrules 22 and 23 respectively and may easily be removed for cleaning purposes. In Fig. 3 is further shown how the cover 3 has an opening sufficiently large to allow the starting button I 4 to pass. The starting button l4 extends downward and carries the drum 24 with slots 25 and is carried in turn by the motor shaft 26 extending through the bushing 21 held by nut 28 and washer 29 against the spacer 30, this spacer resting on the plate 3| which is the mounting plate of the motor. Further is shown the plate 32 which is a part of the pointer l6 and has for reasons shown below circular detents or rings 33; 34 is the rotor of the synchronous motor, 35 is the coil and 36 the core. The motor mounting plate 3| has a raised lip which engages in a hole in the bottom of housing 2 thus preventing the stator of the synchronous motor the motor to rotate except when the housing 2 is turned. v

In Fig. 4 is shown a sectional elevation of the watch holder l, and it illustrates how the holder closes by the force of spring I around any object placed between its jaws. It is alsoshovwn how again is the bearing for arm Q. As the latter arm is revolvable in both I and I as well as around the telescope'l it can easily be adiusted so that the line of vision of the telescope I ialls directly on the balance wheel of the watch held in holder 8.

The operation of the device is as follows: A watch or watch movement is placed in holder l which is adjusted so that the line of vision of the telescope I falls directly on the balance wheel of the watch. The switch I. is then turned and the motor is started by button It, this also lights lamp I. which focuses a strong light on the balance wheel of the watch to be tested. The rotor of 34 has 48 teeth N and will therefore-with a 60 cycle current make 150 revolutions per minute, on currents of diiIerent frequencies a different number of teeth is required. The relation between the number of teeth 34', frequency and speed of rotation is such that for each half cycle of current the rotor II is advanced one tooth 34'. The interrelation between these thrce quantities may be conveniently expressed in the following equation:

In this equation n is the number of revolutions per minute, I is the number of cycles per second and p the number of teeth of the rotor 34. The standard watch movement makes 300 swings per minute so that the speed of revolutions per minute of the motor corresponds to the number of complete cycles of the balance wheel. The motor revolves the drum 24 with the speed of 150 R. P. M. 'Ifh's drum is eccentrlcally slit with openings 25 in such manner that once for every revolution of the drum one may see through the telescope I and obtain a glimpse oi the balance wheel of the watch. As the balance wheel is seen only once for every complete cycle it makes it will appear to be standing still, i. e. when the watch is synchronized with the motor. The pointer I6 is now set on ii on the dial I5 and by holding the telescope and turning the motor housing one way or the other synchronism is obtained. The direction in which the motor housing, and motor stator, has to be turned indicates at once if the watch is leading or lagg fl. if the watch is lagging the pointer 16 and thereby the motor must be turned in the opposite direction to the rotation of the motor, and ii the watch is leading the pointer must be moved in the direction of the rotation of the motor. By observing the motion required to keep the watch synchronfired during a definite interval 0! time it is possible with great accuracy to predict the error of the watch. To this end the dial I5 is divided in 288 divisions and by calculation it may be shown that for a two minute interval each division on the dial corresponds to one second error per twenty-four hours. It is also, of course, posible to calibrate the dial to any other desired time interval and unit of time comparison. After the pointer is set on zero and synchronism is obtained this condition is upheld by slowly turning the pointer along the dial it during a two minute interval, at the end of which time the dial is read cular dents or rings 88 so as to how much watch is leading or lagging. The pointer II is part of plate 32 which has cirplaced that when the pointer I. is moved the plate It turns and exert! greater friction one way than the other so-that. the stator will follow as the pointer'is turned.

By lengthening the time of observation the accuracy of the error determination will be greatly increased. I have found, however. that for practical purp s a period 0! two minutes is entirely The first test may, of course. be much shorter period of time.

to adiust a watch in two or three settings.

Having thus described claim is: f

1. In a portable instrument for the location and determination of faults or errors in watches the combination of a support having a telescope mounted thereon for observing an part of a watch, a holder movably supported on and adjustable around said telescope for holding the time piece in various positions, a stroboscopic shutter rotatably'mounted on said support and positioned telescope, a synchronous motor rotatably mounted on said-support for rotating said shutter, a dial rigidly mounted upon said support, an indicator connected by a frictional connection to the stator of said synchronous motor to indicate its position relative to said fixed dial.

2. In a portable instrument for the location and determination of faults or errors in watches the combination of a support having a telescope mounted thereon for observing an oscillating part of a watch, a holder movably supported on and adjustable around said telescope for holding the time piece in various positions, a strobeinvention what I scopic shutter rotatably mounted on said support and having two eccentrically located slots so positioned as to intercept the line of vision of said telescope once for every revolution of said shutter, a synchronous motor rotatably mounted on said support for rotating said shutter, a dial rigidly mounted upon said support, an indicator connected by a frictional connection to the stator of said synchronous motor to indicate its position relative to said fixed dial.

3. In a portable instrument for the location and determination of faults or errors in watches the combination of a support having a telescope mounted thereon for observing the balance wheel of a watch, a holder movably supported on and adjustable around said telescope for holding the time piece in various positions, a stroboscopic shutter rotatably mounted on said support and having two eccentrically located slots so positioned as to intercept the line of vision of said telescope once for every revolution, a nonselfstarting type synchronous motor rotatably mounted on said support for rotating said shutter, at a fixed speed, a dial rigidly mounted upon said support and having graduations in seconds per 24 hours slow or last, an indicator connected by a frictional connection to the stator of said synchronous motor whereby the relative time difference between the time piece tested and the standard time as given by the regulated frequency driving the synchronous motor may be directly in seconds per 24 hours.

sun- A. W108.

Askilledwatchmakerwill, 

